RE: Important: Oracle processes taking lots of CPU
- From: "Cary Millsap" <cary.millsap@xxxxxxxxxx>
- To: <ORACLE-L@xxxxxxxxxxxxx>
- Date: Wed, 24 Nov 2004 13:21:58 -0600
Both the time spent in user mode (%usr) spinning for a latch and the =
time
spent in kernel mode (%sys) contribute to the c statistic shown in =
extended
SQL trace files.
If your system is enduring a lot of preemptions (context switching), you =
can
also detect that in your extended SQL trace data by noticing that a
significant proportion of your total response time is unaccounted for. =
You
can detect unaccounted-for time in your extended SQL trace data, but I =
don't
think there's any way to detect it Oracle's V$/X$ data.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
* Nullius in verba *
Upcoming events:
- Performance Diagnosis 101: 1/4 Calgary
- SQL Optimization 101: 11/8 Dallas, 12/13 Atlanta
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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx =
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of John Kanagaraj
Sent: Wednesday, November 24, 2004 1:13 PM
To: 'New DBA'; ORACLE-L@xxxxxxxxxxxxx
Subject: RE: Important: Oracle processes taking lots of CPU
Hi New DBA,
>As I understand, the CPU is used while performing
>LIOs, doing calculation, sorts or while spinning for
>the latches. My understanding might be wrong! Since
>there aren't enough LIOs or complex calculations
>involved I thought that spinning for latches might be
>causing excessive CPU.=20
Spinning does cause CPU issues. I believe that if you have many =
processes
and comparatively lesser number of processors, then you might have a lot =
of
CPU consumption that is unaccounted for as cycles used for process =
context
switching is not accounted in oracle. You will have to then look at 'sar =
-u'
( look for high %sys), 'sar -q' (look for high run queue size and =
occupancy)
and 'sar -w' (look for excessive process switches).
Let us know if this helps,
John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)
http://tahiti.oracle.com - Manuals for DBAs (English only)
http://www.bibleserver.com - Manual for Life (in English, Deutsch, =
French,
Italian, Spanish, Portugese, Turkish,...)
** The opinions and facts contained in this message are entirely mine =
and do
not reflect those of my employer or customers **
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